This invention relates to a loading hose for use in a paper machine doctor or coating device, which loading hose lies between the doctor""s or coating device""s blade supports and rotatable blade holder. The loading hose is arranged to load the blade of the doctor or the coating blade of the coating device, and has a flexible, pressure-resistant casing of uniform cross-section.
In a hose-loaded doctor in a paper machine, the contact force of the doctor blade on the surface of the roll being cleaned, or, in coating devices, the contact force of the coating blade on the surface being coated, is increased by means of loading hoses acting on the blade holder. Generally, two loading hoses are used in the blade holders in question. The parts of the doctor and the loading hoses are arranged so that one loading hose loads the blade and the other releases it. The return movement loading hose can also be used to create a counter-pressure, allowing a higher and more easily regulated pressure to be used in the loading hose. This is important, because the essential factor in adjustment and loading is the pressure difference, and not the pressure level. The usual pressure medium is air.
Loading hoses normally have an oval cross-section. The loading hose is set between the turning blade holder and its support. Generally, the loading hose is supported by its widest sides against the support surfaces. Over a certain distance, the loading hose operates as desired, in other words, the thickness of the hose increases, while its width remains essentially the same. However, in known loading hoses, this operational distance is short, and, as the distance between the support surfaces increases further, the loading hose assumes an increasingly round shape. In this case, the force created by the loading hose suddenly drops, which is extremely disadvantageous in terms of loading. In addition, known loading hoses are flexible in all directions, so that when the loading varies they move between the blade holder and the support and can even hang partly outside these. This causes variations in the loading force over the length of the doctor. In addition, when the blade returns, the part of the loading hose that is hanging loosely can be squeezed, and even broken, between the parts of the doctor or coating device.
The present invention provides a new type of loading hose for use in the doctor or coating device of a paper machine, which eliminates the defects of the prior art and creates the desired loading profile in the blade.
More specifically, the present invention provides a loading hose for use in a paper machine doctor or coating device, which loading hose is located between the doctor""s or coating device""s blade support and rotatably arranged blade holder. The loading hose is arranged to load the doctor blade of the doctor or the coating blade of the coating device, and incorporates a flexible casing, which is pressure-resistant and of a uniform cross-section. The loading hose includes at least one stiffening member attached to the casing, which is arranged to lie against one of the blade support or the blade holder.
The stiffening member comprises stiffening plates, at least one of which is manufactured from a composition material to create a friction or sliding effect. Alternatively, the stiffening member comprises stiffening plates, on top of one of which a layer is arranged to create a friction or sliding effect. The layer may comprise friction or sliding plates, which are narrower than the stiffening plate or the friction or sliding plates may comprise at least two narrow parts.
In yet another arrangement the layer is a surfacing.
Additional plates may be provided inside the loading hose at the location of the stiffening members, the width of which is essentially the same as that of the stiffening members.
Part of the cross-section of a loading hose according to the invention is rigid, so that it cannot become detrimentally rounded. The hose is also stiff enough longitudinally to ensure that it remains in place, even if contact is lost with the support surfaces. This makes it less probable that the hose will hang loosely and be broken. In addition, there is less variation in the level of force arising from changes in the distance between the moment point and the loading hose. The loading profile of the blade also remains as desired over the entire length of the doctor or coating device while the installation of the loading hose is facilitated. In addition, the friction properties of the loading hose can be altered if required, which also facilitates installation, among other things.
These and other features and advantages of the invention will be more fully understood from the following detailed description of the invention taken together with the accompanying drawings.